Turkish police officers issued arrest warrants for 53 suspects on Friday and arrested 39 of them for their suspected links to Fetullah Terrorist Organization (FETO), the group behind the 2016 defeated coup attempt, security sources said.

The Chief Public Prosecutor’s office in Turkey’s capital city Ankara issued warrants for 53 suspects who are accused of using the terror group’s encrypted smartphone messaging app, ByLock.

Read more: Turkey: 39 FETO suspects arrested in capital Ankara